Chapter 18 Renewable EnergyChapter 18 Renewable Energy18-1 Renewable Energy Today18-1 Renewable Energy Today

Renewable EnergyRenewable Energy: from sources that are : from sources that are constantly being formed (ex. solar, wind, constantly being formed (ex. solar, wind, moving water, Earth’s heat)moving water, Earth’s heat)

I. Solar Energy – Power from the I. Solar Energy – Power from the SunSun

1.1. Passive Solar Heating: uses the sun’s Passive Solar Heating: uses the sun’s energy to heat something directlyenergy to heat something directly

– Passive Solar HomesPassive Solar Homes– Large south-facing windowsLarge south-facing windows– Well insulatedWell insulated– Overhanging roofOverhanging roof

-summer = sun’s path is high in -summer = sun’s path is high in the sky (roof provides shade)the sky (roof provides shade)

-winter – sun’s path is lower in the -winter – sun’s path is lower in the sky (sunlight can shine into the sky (sunlight can shine into the home)home)

Passive Solar HomePassive Solar Home

Active Solar Heating:Active Solar Heating: energy energy from the sun is gathered by from the sun is gathered by collectors and used to heat water collectors and used to heat water or to heat a buildingor to heat a building

Photovoltaic CellsPhotovoltaic Cells

Photovoltaic Cells:Photovoltaic Cells: solar cells – solar cells – convert sun’s energy into convert sun’s energy into electricityelectricity Produces a very small electrical currentProduces a very small electrical current A small city would need hundreds of A small city would need hundreds of

acres of solar panels acres of solar panels Require extended periods of sunshineRequire extended periods of sunshine Energy has to be stored in batteries or Energy has to be stored in batteries or

fed back into the grid (net-metering)fed back into the grid (net-metering) Becoming increasingly efficient & less Becoming increasingly efficient & less

expensiveexpensive Great potential in developed countries, Great potential in developed countries,

where energy consumption is minimalwhere energy consumption is minimal

Wind FarmWind Farm

II. Wind Power – Cheap & II. Wind Power – Cheap & Abundant Abundant Wind moves a turbine to generate electricityWind moves a turbine to generate electricity Fastest growing energy source in the worldFastest growing energy source in the world Wind Turbines are cost effective and can be built Wind Turbines are cost effective and can be built

in 3 monthsin 3 months Wind Farms:Wind Farms: large arrays of wind turbines large arrays of wind turbines Turbines take little spaceTurbines take little space

– Some farmers add wind turbines to their land Some farmers add wind turbines to their land and sell the electricityand sell the electricity

An underdeveloped resourceAn underdeveloped resource – scientists – scientists estimate that the windiest spots on Earth could estimate that the windiest spots on Earth could generate more than 10 times the energy used generate more than 10 times the energy used worldwideworldwide

ProblemProblem = transporting electricity from rural = transporting electricity from rural areas where it is generated to urban centersareas where it is generated to urban centers

III. BiomassIII. Biomass – power from living – power from living thingsthings Biomass fuel: any organic matter that is used as Biomass fuel: any organic matter that is used as

an energy source (plant material, manure, etc.)an energy source (plant material, manure, etc.) Fossil fuels don’t count because they are Fossil fuels don’t count because they are

nonrenewablenonrenewable Wood & Dung are major sources of energy in Wood & Dung are major sources of energy in

developing countriesdeveloping countries Although wood is renewable – it can result in Although wood is renewable – it can result in

habitat loss, deforestation, and soil erosion if habitat loss, deforestation, and soil erosion if trees are cut down faster than they can growtrees are cut down faster than they can grow

Burning wood & dung can release harmful air Burning wood & dung can release harmful air pollutionpollution

BiofuelsBiofuels

1.1. MethaneMethane: produced when bacteria : produced when bacteria decompose organic wastesdecompose organic wastes

– Burn it to make heat / electricityBurn it to make heat / electricity– China ferments manure to make gas for heating & China ferments manure to make gas for heating &

cookingcooking– Britain opened a dung-fired power plant in 2002 Britain opened a dung-fired power plant in 2002 – Some landfills generate electricity w/ methane Some landfills generate electricity w/ methane

made from decomposing trashmade from decomposing trash

2.2. AlcoholAlcohol EthanolEthanol – made by fermenting fruit or – made by fermenting fruit or

agricultural wasteagricultural waste Corn is a major source in the USCorn is a major source in the US GasoholGasohol: gasoline + ethanol : gasoline + ethanol

– produces 28% less emissions than fossil fuels, but produces 28% less emissions than fossil fuels, but produces 38% less energyproduces 38% less energy

DAMDAM

IV. HydroelectricityIV. Hydroelectricity – Power – Power from Moving Waterfrom Moving Water Hydroelectric Energy:Hydroelectric Energy: produced from produced from

moving watermoving water– Dam is built across a river to hold back a Dam is built across a river to hold back a

reservoirreservoir of water of water– Water is released to turn a turbineWater is released to turn a turbine– Turbine spins a generator to produce Turbine spins a generator to produce

electricityelectricity

DAMDAM

Benefits:Benefits:– Expensive to build, but inexpensive to operate & last Expensive to build, but inexpensive to operate & last

longer than fossil-fuel powered plantslonger than fossil-fuel powered plants– No air pollutantsNo air pollutants– Flood controlFlood control– Water for drinking, agriculture, industry, recreationWater for drinking, agriculture, industry, recreation

Disadvantages:Disadvantages:– Changes a river’s flowChanges a river’s flow– Reservoir floods large areas of habitat above the Reservoir floods large areas of habitat above the

damdam– People are often displacedPeople are often displaced– Water flow below the dam is reduced – disrupting Water flow below the dam is reduced – disrupting

ecosystems downstreamecosystems downstream– Prevents salmon from swimming upriver to spawnPrevents salmon from swimming upriver to spawn– As river slows, it deposits sediment behind the dam As river slows, it deposits sediment behind the dam

instead of enriching the land farther downstreaminstead of enriching the land farther downstream– Plant matter decaying in reservoirs can release large Plant matter decaying in reservoirs can release large

amounts of greenhouse gassesamounts of greenhouse gasses

Modern Trends - Micro-Modern Trends - Micro-hydropowerhydropower– Electricity produced in a small stream Electricity produced in a small stream

w/out a big damw/out a big dam– Turbine may even float and not block the Turbine may even float and not block the

river at all!river at all!

V. Geothermal EnergyV. Geothermal Energy – Power – Power from the Earthfrom the Earth Energy from heat in the Earth’s crustEnergy from heat in the Earth’s crust In some areas, deposits of water in the In some areas, deposits of water in the

Earth’s crust are heated by energy within Earth’s crust are heated by energy within the Earththe Earth

Geothermal Power PlantsGeothermal Power Plants pump pump heated water or steam from rock heated water or steam from rock formations and use the water or steam to formations and use the water or steam to power a turbine – the water is usually power a turbine – the water is usually returned to the crustreturned to the crust

Geothermal Heat PumpsGeothermal Heat Pumps: : Energy for HomesEnergy for Homes– Temp. of the ground is nearly Temp. of the ground is nearly

constant year-roundconstant year-round– Geothermal heat pumpGeothermal heat pump – uses – uses

stable underground temp. to warm stable underground temp. to warm and cool homesand cool homes Simply a loop of piping that circulates a Simply a loop of piping that circulates a

fluid undergroundfluid underground

18-2 Alternative Energy and 18-2 Alternative Energy and

ConservationConservation Alternative EnergyAlternative Energy: energy sources that : energy sources that

are still in developmentare still in development Must beMust be

– Cost effectiveCost effective– Acceptable environmental effectsAcceptable environmental effects

Government investment is often the only Government investment is often the only way to research some of these way to research some of these possibilities. possibilities.

Tidal PowerTidal Power Works like a hydroelectric damWorks like a hydroelectric dam

Tide rises, water flows behind a damTide rises, water flows behind a dam Sea level falls trapping water behind the damSea level falls trapping water behind the dam Reservoir is released to turn a turbineReservoir is released to turn a turbine

Used in France, Russia, and CanadaUsed in France, Russia, and Canada ProsPros: renewable, non-polluting: renewable, non-polluting ConsCons: high cost of building and : high cost of building and

maintaining, few locations are suitablemaintaining, few locations are suitable

Ocean Thermal Energy Conversion Ocean Thermal Energy Conversion (OTEC)(OTEC)1.1. Warm surface water used Warm surface water used

to boil sea water (boils at to boil sea water (boils at low temp. at low pressure low temp. at low pressure in a vacuum chamber)in a vacuum chamber)

2.2. Steam turns turbineSteam turns turbine

3.3. Deep, cold ocean water Deep, cold ocean water cools the steam to make cools the steam to make reusable waterreusable water

not cost effective (so far)not cost effective (so far) environmental effects environmental effects

unknownunknown

Hydrogen – A Future Fuel Source?Hydrogen – A Future Fuel Source? The most abundant element in the universeThe most abundant element in the universe Can be burned as a fuelCan be burned as a fuel Does not release pollutants associated w/ burning fossil fuels and Does not release pollutants associated w/ burning fossil fuels and

biomassbiomass When hydrogen is burned, it combines with oxygen to produce water When hydrogen is burned, it combines with oxygen to produce water

vapor and small amounts of nitrogen oxidesvapor and small amounts of nitrogen oxides Can be produced by using electricity to split molecules of waterCan be produced by using electricity to split molecules of water

The Challenge of Hydrogen:The Challenge of Hydrogen: Takes a lot of energy to produceTakes a lot of energy to produce 1 alternative: use electricity from solar cells or wind power to split 1 alternative: use electricity from solar cells or wind power to split

water molecules to produce hydrogen water molecules to produce hydrogen then store it in pressurized then store it in pressurized tanks and transport it in pipelinestanks and transport it in pipelines

Fuel CellsFuel Cells: produces electricity chemically (like a battery): produces electricity chemically (like a battery) Combines hydrogen fuel w/ oxygen from the airCombines hydrogen fuel w/ oxygen from the air Electricity is producedElectricity is produced Water is the only byproductWater is the only byproduct Can be fueled by anything that contains plenty of hydrogen (natural Can be fueled by anything that contains plenty of hydrogen (natural

gas, alcohol, gasoline)gas, alcohol, gasoline) Soon portable electronics (phones, games) may be powered by Soon portable electronics (phones, games) may be powered by

micro-fuel cells (fueled w/ alcohol) micro-fuel cells (fueled w/ alcohol) no charging or changing no charging or changing batteries batteries

Energy EfficiencyEnergy Efficiency: the percentage of : the percentage of energy put into a system that does useful energy put into a system that does useful workwork Energy efficiency (in %) = energy out/energy in Energy efficiency (in %) = energy out/energy in

X 100X 100

Efficient TransportationEfficient Transportation

Developing efficient enginesDeveloping efficient engines Increasing the use of public Increasing the use of public

transportation systemstransportation systems

Hybrid CarsHybrid Cars Energy-efficient vehicles currently in useEnergy-efficient vehicles currently in use Use a small, efficient gasoline engine most of the timeUse a small, efficient gasoline engine most of the time Also use an electric motor when extra power is needed Also use an electric motor when extra power is needed

(i.e. accelerating)(i.e. accelerating) Converts some of the energy of braking into electricity Converts some of the energy of braking into electricity

(stored in battery)(stored in battery) Sometime shut off the gasoline engine (i.e. when Sometime shut off the gasoline engine (i.e. when

stopped at a red light)stopped at a red light) Cost less to refuelCost less to refuel Produce less harmful Produce less harmful EmissionsEmissions

VIDEO

Cogeneration:Cogeneration: the production of 2 useful forms of the production of 2 useful forms of energy from the same fuel sourceenergy from the same fuel source

i.e. waste heat from an industrial furnace can i.e. waste heat from an industrial furnace can power a steam turbine that produces electricitypower a steam turbine that produces electricity

Energy ConservationEnergy Conservation: saving energy: saving energy Using energy-efficient devices, wasting less Using energy-efficient devices, wasting less

energyenergy Using less of any resource usually translates into Using less of any resource usually translates into

saving energysaving energy Most of the energy lost from homes is lost Most of the energy lost from homes is lost

through poorly insulated windows, doors, walls, through poorly insulated windows, doors, walls, and the roofand the roof

Replace old windows w/ new high efficiency windowsReplace old windows w/ new high efficiency windows Seal gaps around doors and windows with caulking or weather Seal gaps around doors and windows with caulking or weather

strippingstripping

Ways to Save Energy Around The Ways to Save Energy Around The

HouseHouse